Cube Satellites (CubeSats) are considered the satellites of the future because they are small, low cost, and easy to build. Due to these features many universities and private companies utilize them for research purposes and performing experiments in Lower Earth Orbit (LEO). Small satellite systems are useful for precision work such as formation flying, high resolution imaging, and interferometry because these tasks require small thrust levels to finely actuate the CubeSat position.
Although small satellite systems technology has many benefits, it is held back by its lack of propulsion, and therefore the inability to maneuver itself. The CubeSat boom of the late 1990s and early 2000s has further brought a call for small propulsion systems to outfit these miniature satellites. If they have the ability to orient and propel themselves, CubeSats can be utilized for a wider variety of missions.
Micro electric propulsion systems are an excellent candidate for remedying the lack of propulsion in these small satellite systems, and the Micro-propulsion and Nanotechnology Laboratory (MpNL) of The George Washington University (GWU) has spent the past decade designing micro-thrusters to solve the miniature propulsion system problem.
The Micro-Cathode Arc Thruster (μCAT) system to propel CubeSats was constructed by MpNL to address the problem. The μCAT allows CubeSats to control their attitude, actuation, orbit change, de-orbiting, and movement at a maximum specific impulse of 3000 s. The standard μCAT comprises two electrodes, a cathode and an anode. An arc is created between the two electrodes from an electric pulse sent by a power processing unit (PPU).
The MpNL collaborated with the United States Naval Academy (USNA) to launch the first round of μCATs on a 1.5 U CubeSat to monitor their performance. Four μCATs are integrated into the USNA's Ballistically Reinforced Communication Satellite (BRICSat-P) to perform three maneuvers while at a 500 km orbit. The three maneuvers are: de-tumbling, spin maneuvers, and a delta-v maneuver.
The thruster system is comprised of four thruster heads with their respective PPUs mounted on two thruster head boards and a control unit. Each thruster head faces in the same direction to allow the BRICSat-P to control rotation in the x and z axes. The thruster heads (100) can be seen in FIG. 1.
USNA performed a full functionality test in vacuum by suspending the CubeSat from the ceiling of the chamber, winding the wire around 5 times, and then releasing it to simulate de-tumbling. The wire is wound for the axes of rotation to be in the opposite direction of the thruster firing. Results show that the thrusters firing in the opposite direction slow the rotation rate and accurately control the de-tumbling.
The standard μCAT, which was used on board the BRICSat-P, utilizes a spring system to move the cathode forward to replenish the propellant. The flown design consists of the electrodes seated concentrically with the anode at the center surrounded by a dielectric buffer the cathode encircling the two. See for instance, U.S. Pat. Nos. 8,875,485 and 9,517,847.